A number of standards for asynchronous data transmission (e.g., International Telecommunication Union—Telecommunication Standardization Sector (ITU-T) G.705, G.707, G.709, and the like) define data frame mapping schemes for multiple hierarchies. The ITU-T G.705 standard defines various Plesiochronous Digital Hierarchy (PDH) applications utilizing different data rates for each hierarchy. The G.707 (G.modem) standard describes transport of optical data unit (ODU) signals using virtually concatenation. The G.709 standard defines time division multiplexing (TDM) and constant bit rate (CBR) multiplexing using various hierarchies of an optical transport network (OTN). Furthermore, the jitter generation requirements for equipment associated with such networks are defined in associated ITU-T standards (e.g., ITU-T G.824, G.825, G.825.1, and similar standards).
As opposed to networks using synchronous systems (e.g., Synchronous Digital Hierarchy (SDH), where the frequency of Synchronous Transfer Mode (STM) Level 4 (STM4) is four times the frequency of STM1), the data rates of asynchronous transmission systems are not integer multiples. For example, the data rate of ODU2 is approximately equal to (238/237)*4 times the data rate of ODU1. Since PDH, OTN, and like signals do not support pointer mechanisms, stuffing (e.g., a bit for PDH, a byte for OTN, and the like) is needed in order to map multiple client signals with different frequency drift in a single bit stream. For demapping of the client signals, a desynchronizer is necessary to meet the jitter requirements.
The existing method of demapping requires an external analog phase-locked loop for each data channel and each hierarchical level. As such, a large number of external analog phase-locked loops is often required for demapping client signals. This large number of analog phase-locked loops is expensive in terms of space (e.g., large printed circuit boards are required for demapping), component reliability, system reliability, power consumption, crosstalk, device cost, and associated parameters. Furthermore, a single step desynchronizer approach is not possible due to the data frames of the differing hierarchies drifting against each other. Thus, a single step implementation would actually result in additional low frequency jitter and wander.